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Abstract:

Wireless microphones are used in a plurality of applications, such as
concerts, discussions, theater performances, operas, etc. The wireless
microphones are normally connected to a transmitter which transmits the
audio signals captured by the microphone to a base station via a
transmitting frequency. The invention relates to a microphone system (1)
having a base station (3) and having a microphone module (2) wherein the
base station (3) is designed to wirelessly receive audio information
and/or test information transmitted from the microphone module (2) on an
operating frequency, wherein the base station (3) has a receiving
analysis module (14) and/or is coupled thereto, which is designed to
analyze the reception quality of the audio information and/or the test
information on a plurality of possible transmitting frequencies, wherein
the receiving analysis module (4) is designed to select the operating
frequency from the plurality of possible transmitting frequencies.

Claims:

1. A microphone system (1) having a base station (3) and having a
microphone module (2), wherein the base station (3) is designed to
receive information, transmitted on an operating frequency, wirelessly
from the microphone module (2), wherein the base station (3) has a
reception analysis module (14) and/or is coupled to the reception
analysis module (14) which is designed for analyzing the quality of
reception of the information at a number of possible transmitting
frequencies, characterized in that the reception analysis module (14) is
designed for selecting the operating frequency from the plurality of
possible transmitting frequencies.

2. The microphone system (1) as claimed in claim 1, characterized in that
the information is designed as digital signals.

3. The microphone system (1) as claimed in claim 2, characterized in that
the quality of reception is analyzed on the basis of a bit error rate and
a channel bit error rate.

4. The microphone system (1) as claimed in claim 1, characterized by a
frequency analysis module (21) which is designed for analyzing a
frequency spectrum for free transmitting frequencies.

5. The microphone system (1) as claimed in claim 1, characterized in that
a return channel (9), which is designed for transmitting an information
item about the operating frequency, can be activated between the base
station (3) and the microphone module (2).

6. The microphone system (1) as claimed in claim 1, characterized by a
plurality of microphone modules (2) and base stations (3), characterized
by a central control device (23) for issuing of the operating frequencies
for the microphone module (2)--base station (3) allocation.

7. The microphone system (1) as claimed in claim 1, characterized by a
control device (23) which is designed for holding a list of free
transmitting frequencies and distributing operating frequencies, taking
into consideration intermodulation products of the operating frequencies.

8. A method for selecting an operating frequency for a microphone system
(1) having at least one base station (3) and at least one microphone
module (2), wherein the base station (3) is designed to receive
information, transmitted wirelessly on an operating frequency, from the
microphone module (2), wherein the a quality of reception is analyzed at
a plurality of transmitting frequencies, characterized in that the
operating frequency is selected automatically from the plurality of
transmitting frequencies, taking into consideration the quality of
reception.

9. The method as claimed in claim 8, characterized in that the
transmitting frequency spectrum is analyzed for free transmitting
frequencies, wherein the quality of reception of only the free
transmitting frequencies is analyzed subsequently.

10. A computer program having program code for carrying out all the steps
of the method as claimed in claim 8 when the program is executed on a
computer.

11. The microphone system (1) as claimed in claim 1, characterized in
that the information is audio information and test information.

12. The microphone system (1) as claimed in claim 1, characterized in
that the information is audio information.

13. The microphone system (1) as claimed in claim 1, characterized in
that the information is test information.

14. The microphone system (1) as claimed in claim 2, characterized in
that the quality of reception is analyzed on the basis of a bit error
rate.

15. The microphone system (1) as claimed in claim 2, characterized in
that the quality of reception is analyzed on the basis of a channel bit
error rate.

16. The microphone system (1) as claimed in claim 6, characterized in
that the central control device (23) allocates and controls the order of
issuance of the operating frequencies.

17. The microphone system (1) as claimed in claim 6, characterized in
that the central control device (23) allocates the order of issuance of
the operating frequencies.

18. The microphone system (1) as claimed in claim 6, characterized in
that the central control device (23) controls the order of issuance of
the operating frequencies.

19. The method as claimed in claim 8, characterized in that the
information is audio information and/or test information.

20. A computer program having program code for driving the microphone
system (1) as claimed in claim 1 when the program is executed on a
computer.

Description:

BACKGROUND

[0001] The invention relates to a microphone system having a base station
and having a microphone module, wherein the base station is designed to
receive audio information and/or test information, transmitted on an
operating frequency, wirelessly from the microphone module, wherein the
base station has a reception analysis module and/or is coupled to the
latter which is designed for analyzing the quality of reception of the
audio information and/or of the test information at a number of possible
transmitting frequencies. The invention also relates to a method for
selecting an operating frequency for such a microphone system and a
computer program.

[0002] Wireless microphones are used in a plurality of applications such
as concerts, discussions, theater performances, operas etc. The wireless
microphones are usually connected to a transmitter which transmits the
audio signals captured by the microphone to a base station via a
transmitting frequency. Starting from the base station, the audio signals
are then forwarded to recording devices, amplifiers etc. In the case of
larger events, it is quite normal that a multiplicity of such wireless
microphones are used. Considering, for example, a concert, more than 40
or 50 wireless microphones are often used in parallel operation. Due to
this parallel operation, the necessity arises to match the transmitting
frequencies of the individual wireless microphones to one another in such
a manner that a separate channel is allocated to each wireless
microphone. The installation of the wireless microphones is thus involved
and complicated.

[0003] In printed document DE 10035824 A1 which may well form the nearest
prior art, a system for controlling mobile transmitting and/or receiving
devices connected wirelessly to a central processing unit is described.
The central processing unit and the transmitting and/or receiving devices
are connected via means for bidirectional communication providing for a
simple configuration of the transmitting and/or receiving devices. By
means of the system, a higher-level administration, selection and control
of the operating parameters of the wireless transmission links is
possible.

SUMMARY

[0004] In its general embodiment, the invention relates to a microphone
system which has at least one base station and at least one microphone
module. Base station and microphone module are designed in such a manner
that audio information and/or test information transmitted from the
microphone module via an operating frequency can be received by the base
station. The microphone module is subdivided into a microphone section
which is designed for picking up audio signals and a transmitter section
which handles the wireless communication with the base station. In
particular, the microphone module is designed to be portable. The base
station is preferably designed to be stationary and has preferably an
interface such as, for example, an audio interface, a USB interface, DECT
interface or the like in order to forward the audio signals e.g. on an
amplifier or to a recording device. The audio information reproduces the
audio signals and is designed, for example, as coded audio signals. The
test information is artificial test sequences which do not necessarily
have to correspond to an audio signal.

[0005] The base station has a reception analysis module and/or is coupled
to the latter. The reception analysis module is designed for analyzing
the quality of reception, and hence the quality of transmission of the
audio information and/or of the test information which has been
transmitted by the microphone module, at a number of possible
transmitting frequencies. It is thus possible that the microphone module
transmits the information via various transmitting frequencies, for
example in a test, and the reception analysis module analyzes, and thus
determines and/or quantifies as a parameter, the respective quality of
reception.

[0006] According to the invention, it is proposed that the reception
analysis module is designed for selecting the operating frequency from
the plurality of possible transmitting frequencies. In particular, the
selection is automated and/or based on the qualities of reception of the
transmitting frequencies.

[0007] The invention is based on the concept that it is advantageous if
the selection of the operating frequency does not take place by means of
a trial-and-error method but by means of an objective selection method,
and/or in automated manner. This improves the selection, reduces the
setup time of the microphone system and, in the end, optimizes the
quality of reception of the microphone system set up. In particular, the
quality of reception, and thus the quality of transmission between the
microphone module as transmitter and the base station as receiver is
taken into consideration as a basis for decision. The assessment of the
quality of reception and thus of the quality of transmission is
distinctly more reliable than a pure measurement of the interference
power at the base station. The reason for this is that the spectral form
and the behavior of an interference signal with time are also a part of
the quality of reception, and not only their power. At the same power as
an interference signal of wider bandwidth, a narrow-band interferer such
as, for example, a sinusoidal carrier has fewer effects on the quality of
reception and thus the quality of transmission.

[0008] In a further development of the invention it is provided that the
audio information and/or the test information is designed or transmitted,
respectively, as digital signals. Such digital signals allow high control
of the transmission quality in that transmission parameters such as,
e.g., the compression and/or the redundancy of the signals transmitted
can be adapted with respect to the initial signals. Furthermore, the
transmission of digital signals enables the test information to be
designed as a test sequence which is preferably already known to the base
station so that a high-quality assessment of the quality of reception is
possible.

[0009] In a particularly preferred embodiment of the invention, the
quality of reception is analyzed on the basis of a bit error rate, a bit
error ratio and/or on the basis of a channel bit error rate. The bit
error rate or the bit error ratio, respectively, is determined in that
the base station, as receiver, compares a known bit sequence transmitted
as test information or test sequence with a stored bit sequence and
determines missing or wrong bits and determines from the number or
temporal distribution the respective error parameter and thus the quality
of reception. As an alternative or additionally, the base station as
receiver, can decode the transmitted bit sequence first and then encode
it again and compare it with the transmitted bit sequence, in the case of
unknown bit sequences in the test information. By means of this
procedure, the so-called channel bit error rate can be estimated which
can also form a basis for analyzing the quality of reception.

[0010] In a possible development of the invention, a frequency analysis
module is provided which is designed for analyzing a transmitting
frequency spectrum for free transmitting frequencies. In this context,
the frequency analysis module can be a component of the microphone module
and/or of the base station and/or of a further component of the
microphone system. It is the task of the frequency analysis module to
detect free undisturbed transmitting frequencies. These free transmitting
frequencies are provided, for example, as a list. The transmitting
frequency spectrum and/or the transmitting frequencies and/or the
operating frequency is advantageously in the VHF/UHF frequency band.
Since these frequency bands are also used by terrestrial television, the
microphone systems are second users of these frequency bands. This means
that the microphone system is only allowed to use free frequencies, that
is to say frequencies not occupied by television, at the application
site. In addition, there may also be disturbances by other electrical
devices on some frequencies. A further interference source are
intermodulations between the microphone modules or intermodulations of
other signals with one another or other signals to the microphone
modules. These disturbances are also detected by the frequency analysis
module and taken into consideration in the detection of free frequencies.

[0011] In a preferred embodiment of the invention, the plurality of
possible transmitting frequencies is selected from the list of free
transmitting frequencies. The analysis of free transmitting frequencies
thus sets a first restriction in the choice of operating frequency and
accelerates the method for selecting the operating frequency.

[0012] In an advantageous development of the invention, at least one
return channel can be activated between the base station and the
microphone module. The connection between microphone module and base
station is thus designed to be not only unidirectional but bidirectional.
The additional return channel issues for transmitting an information item
about the selected operating frequency and/or a free transmitting
frequency. The advantage of this embodiment lies, on the one hand, in
that after the selection of the operating frequency, the latter can be
transmitted in automated manner via the return channel to the microphone
module and can there be adjusted. However, it is also appropriate to
transmit data via the transmitting frequencies to the microphone module
for test purposes so that the microphone module can transmit test
information via the transmitting frequencies in order to test the quality
of reception at these transmitting frequencies.

[0013] If the microphone system has a plurality of microphone modules and
base stations, it is an advantageous development of the invention if the
microphone system has means for allocating and/or controlling the order
in which the operating frequencies are issued for the microphone
module-base station allocation. This is because, in this case, the task
is to allocate the microphone modules to the base stations and to assign
an operating frequency to each allocation without issuing the operating
frequencies twice and/or issuing them into frequency bands which are
disturbed by operating frequencies already issued and/or which could
disturb the operating frequencies already issued. In particular,
disturbances could be based on cross modulations or intermodulation
products. The intermodulation products are formed in the case where two
operating frequencies F1 and F2 are arranged adjacent to one another,
wherein, e.g., the third-order intermodulation products are arranged at
the frequency Fmod=(2*F1-F2) or Fmod=(2*F2-F1). Furthermore, disturbances
can occur in the case of disadvantageous conditions of positioning of the
base station or of the microphone modules, respectively, disadvantageous
transmitting power distribution and adjacent transmitting frequencies.
The management of the operating frequencies or the management of the
sequence of issuance of the operating frequencies can be implemented by
the means.

[0014] In a particularly preferred manner, the microphone system has a
control device as the means which is designed for holding the list of
free transmitting frequencies and distributing the operating frequencies
to the plurality of microphone module-base station allocations, taking
into consideration the intermodulation products. By means of the control
device it is possible to distribute the operating frequencies as a
central device from the free transmitting frequencies in such a manner
that interactions between the individual microphone module-base station
allocations are only lightly developed or are minimized.

[0015] A further subject matter of the invention relates to a method for
selecting an operating frequency for a microphone system, preferably for
a microphone system having at least one base station and at least one
microphone module, wherein audio information or test information is/or
can be transmitted to the base station from the microphone module on an
operating frequency and wherein the quality of reception of a number of
transmitting frequencies is analyzed.

[0016] According to the invention, it is provided that the operating
frequency is selected automatically from the number of transmitting
frequencies, taking into consideration the quality of reception analyzed.
The method once again reflects the inventive concept of providing for an
automatic selection, and thus also optimization of the operating
frequency, from a number of transmitting frequencies.

[0017] After the selection of the operating frequency, the latter is
displayed in a first possibility of the method and must be set manually
by a user on the microphone module. The operating frequency is preferably
set automatically at the base station.

[0018] In a second embodiment of the invention, an information item about
the operating frequency is transmitted to the microphone module so that
the operating frequency is set in automated manner both as transmitting
frequency at the microphone module and as receiving frequency at the base
station.

[0019] In an advantageous development of the invention, the transmitting
frequency spectrum is preferably analyzed for free transmitting
frequencies before the selection of the operating frequency, the quality
of reception only of free transmitting frequencies being subsequently
analyzed. Due to the fact that disturbed or occupied transmitting
frequencies or bands are not analyzed, this section of the method can be
executed more effectively and thus more rapidly.

[0020] Various options are conceivable with respect to the sequence of the
method:

[0021] In a first alternative of the method, all free frequencies are
initially found by the frequency analysis module and transmitted to the
microphone module as transmitter, for example in the form of a table.
Following this, the microphone module transmits a test sequence on all
free frequencies, especially of the table imparted. The reception
analysis module in each case assesses the quality of reception and
selects an operating frequency in dependency on the measured quality of
reception. This operating frequency is imparted to the microphone module
via the return channel and set as receiving frequency by the base
station. The microphone module then sets the selected operating frequency
as transmitting frequency so that audio information can be transmitted.

[0022] In a second alternative of the method, the aforementioned steps are
not processed in the manner of a table but sequentially. In this case, it
is verified from a lesser number or only from one transmitting frequency
whether it is free, and conveyed to the microphone module. The microphone
module transmits on the transmitting frequency conveyed and the reception
analysis module assesses the quality of reception. These two steps are
repeated until all transmitting frequencies or only all free transmitting
frequencies are tested. After that, an operating frequency is selected
again in dependence on the quality of reception measured or analyzed and,
as already mentioned above, transmitted to the microphone module and the
base station.

[0023] In a further alternative of the method, a procedure without return
channel is also conceivable. In this context, it is provided that the
microphone module transmits test frequencies or real audio information in
accordance with a defined pattern, for example in fixed time intervals,
on the transmitting frequencies and/or only on the free transmitting
frequencies. As an alternative to the time intervals, the microphone
module can inform the reception analysis module, e.g. via a transmitted
intermediate information item, when it switches to the next transmitting
frequency. In principle, it is also possible that the microphone module
informs the reception analysis module which transmitting frequency it
will switch to next. The reception analysis module assesses for each
transmitting frequency the quality of reception and selects an operating
frequency in dependence on the quality of reception and represents it at
the operating panel, for example at a display. Following this, the user
sets the operating frequency manually at the microphone module.

[0024] If a number of microphone module-base stations allocations are
initialized, the selected process must be performed for each allocation.
Preferably, test sequences are transmitted on the microphone systems
already supplied with operating frequencies so that the subsequent
microphone systems recognize that these operating frequencies are already
occupied and/or detect intermodulation products of these operating
frequencies.

[0025] In the simplest case, the user must start the process manually for
each allocation. In one development of the invention, the process can be
simplified in that a start signal is forwarded from allocation to
allocation. It is also possible that the sequence is managed and
organized in particular, centrally by the previously described control
device as master unit. In this case, the sequence of installation can
take place as follows:

[0026] In a first step, free transmitting frequencies are detected and
evaluated by the frequency analysis module. In a next step, the quality
of reception and especially the received powers of the individual
allocations are checked, which, in particular, depend on the respective
distance between microphone module and base station. In a next step
following, the control device calculates suitable operating frequencies
for each allocation taking into consideration the quality of reception
and all relevant intermodulation products. In a last step, the operating
frequencies are allocated to the allocations, particularly the microphone
modules and the base stations allocated.

[0027] As an alternative to the simultaneous distribution of the operating
frequencies, an operating frequency can be specified sequentially for
each allocation and this can be imparted to the allocation. Furthermore,
free frequencies can be checked again by the frequency analysis module.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further features, advantages and effects of the invention are found
in the subsequent description of a preferred exemplary embodiment of the
invention and the attached figures, in which:

[0029] FIG. 1 shows a schematic block diagram of a microphone module-base
station allocation as a first exemplary embodiment of the invention:

[0038]FIG. 9 shows a block diagram of a microphone system having a
plurality of allocations with a first option of coordination;

[0039]FIG. 10 shows the microphone system in FIG. 9 in a development as a
next exemplary embodiment of the invention;

DETAILED DESCRIPTION

[0040] Corresponding parts or designations are in each case provided with
mutually corresponding reference symbols.

[0041] FIG. 1 shows a schematic representation of a microphone system 1
which comprises a microphone module 2 and a base station 3. The
microphone module 2 has a microphone section 4 and a transmitting section
5 which can transmit audio signals, picked up with the microphone section
4 via an antenna 6, as audio information wirelessly to the base station
3. The latter receives the audio information by means of a further
antenna 7 reconverts them, if necessary, into audio signals and transfers
these to an audio sink 8 such as, for example, an amplifier, a recording
device and the like. Such microphone systems 1 are used, for example, in
public events such as discussions, plays, concerts etc. The wireless
transmission takes place via an operating frequency Fn.

[0042]FIG. 2 shows an extension of the microphone system 1 in FIG. 1
wherein, apart from the wireless transmission of the audio information
via the operating frequency Fn, a return channel 9 is provided which can
also transmit control signals from the base station 3 wirelessly to the
microphone module 2. For this purpose, the base station 3 has a return
channel transmitter and the microphone module 2 a return channel receiver
11. The information which is transmitted via the return channel 9 is
implemented by a control unit 12 on the side of the base station 3 and a
control unit 13 on the side of the microphone module 2. For example, an
information item about the operating frequency Fn is transmitted via the
return channel 9 so that it can be set by the control unit 13 in
transmitting section 5.

FIG. 3 illustrates the situation when it is not only base station
3--microphone module 2 allocation which is provided but a plurality
thereof. FIG. 3 shows N such allocations. So that the allocations can be
transmitted undisturbed by one another, the operating frequencies Fn1 . .
. FnN must be different. Additionally, the operating frequencies must
have certain distances from one another, particularly in dependency on
the transmitting power of the microphone modules 2 and the local vicinity
to one another.

[0043] This set of problems is illustrated, for example, in FIG. 4a which
shows a graph in which frequency f is plotted highly schematically with
respect to a received power 1 at the base stations 3. Two distributions
around two operating frequencies Fna and Fnb are shown which show a
similar received power 1. As can be seen from the graph, the distance
between the two frequencies is adequate. FIG. 4b in contrast, shows the
situation if the received powers 1 are of quite different strength, the
received power around the operating frequency Fnb being distinctly
greater than the received power 1 around the operating frequency Fna. The
intensity distribution of frequency Fnb distinctly overlaps the intensity
distribution of frequency Fna with one shoulder so that it can be
expected that the operating frequency Fnb interferes with the operating
frequency Fna. In the distribution of the transmitting powers shown, the
distance between frequencies Fna and Fnb has been selected as being too
small. Another possible interference is shown in FIG. 5, wherein, apart
from the main frequency distribution of the operating frequencies Fna and
Fnb, intermodulation products are shown which are located at frequencies
2×(Fna-Fnb) and 2×(Fnb-Fna). At these frequencies, it is not
sensible to position further operating frequencies since these would be
disturbed by the interpolation products.

[0044] FIGS. 6a, b illustrate a first exemplary embodiment of a method for
setting up a microphone system 1, in accordance with FIG. 2 for example.
In a first step, test information is transmitted from the microphone
module 2 to the base station 3 on different transmitting frequencies F1 .
. . F4. A reception analysis module 14 analyzes the quality of reception
and thus the quality of transmission at the different transmitting
frequencies. If the audio information or test information transmitted is
coded digitally, it is possible to use, for example, the bit error rate
or the channel bit error rate as an error magnitude. The determination of
these two parameters is outlined in FIG. 7. Firstly, the signal received
is entered into a demodulator 15 and subsequently conducted into a
channel decoder 16, the redundancy in the signal being utilized for
reducing the error rate. Before the signal is conducted to the audio sink
8, additional audio processing 17 can take place.

[0045] If the microphone module 2 transmits a bit sequence known to the
base station 3, for example during the installation process, the
reception analysis module 14 can determine the bit error rate by means of
a comparison of the known bit sequence with the bit sequence in a bit
error rate calculation module 18 behind the channel decoder 16. In the
case of unknown bit sequences, the reception analysis module 14 can
encode the decoded bit sequence again in a channel encoder 19 after the
channel decoder 16 and compare it with the bit sequence before the
channel decoder 16. By this means, the so-called channel bit error rate
can be estimated by a channel bit error rate module 20.

[0046] On the basis of these error parameters, the reception analysis
module 14 can select a suitable operating frequency and transmits this
operating frequency Fn via the return channel 9 to the microphone module
2 which then sets the operating frequency as the transmitting frequency.

[0047] FIG. 8 shows an extension of the method in FIGS. 6a, b, wherein the
base station 3 additionally has a frequency analysis module 21 or is
coupled to it. The frequency analysis module 21 examines the possible
transmitting frequencies for free transmitting frequencies. In this step,
it is taken into consideration that most microphone systems 1 are
operated in the VHF/UHF frequency band which is also utilized by
terrestrial television. The microphone systems 1 are thus second users of
this frequency band so that the microphone systems 1 must only use free
transmitting frequencies, that is to say those not occupied by
television, at the site where they are used. Additionally, other
disturbances can result from the interactions shown in FIGS. 4a, b and 5.
The frequency analysis module 21 carries out a first selection of free
transmitting frequencies which are transferred to the microphone module
2, for example as a table, so that the test information is transmitted
only and exclusively via the transmitting frequencies determined as being
free by the frequency analysis module 21.

[0048] In the case where no return channel 9 is present such as, for
example, in the microphone system 1 according to FIG. 1, the microphone
module 2 can scan the transmitting frequencies in accordance with a
predetermined pattern or, before changing the transmitting frequency, in
each case convey a corresponding information item to the base station 3
so that the latter measures the quality of reception at the correct
transmitting frequencies. The operating frequency Fn is set at the
microphone module 2, for example by the correspondingly selected
operating frequency Fn being displayed on the base station 3 and a user
having to set it at the microphone module 2.

[0049]FIG. 9 shows a microphone system 1 which, according to FIG. 3,
comprises a plurality of allocations. The base stations 3 are connected
to one another via a network 22 and additionally coupled to a central
control device 23. In this simple embodiment, the control device 23
controls only the order in which the tests are carried out according to
FIGS. 6a, b and 8. Thus, it assigns position 1, for example, to the
allocation in the first row, the latter then being allowed to be the
first one to look for the operating frequency Fn1. Once the process has
been concluded the allocation in the second row is started with position
II etc. In a particularly preferred manner, allocations continuously
transmit test information or audio information after the setting of the
operating frequency so that the disturbances are generated selectively in
the transmitting spectrum according to FIGS. 4b and 5 and are taken into
consideration in the analysis of the quality of reception of the
subsequent allocation. It is also possible that the process is carried
out several time iteratively so that the allocations set first also
obtain an operating frequency which is not impaired by disturbances of
allocations set later.

[0050]FIG. 10 shows a development of the invention wherein the control
device 23 is designed as a master which has both, on the one hand, the
frequency analysis module 21 and examines the transmitting spectrum for
free transmitting frequencies. These are then present centrally as a list
in the control device 23. Once the test cycle for analyzing the quality
of reception has been run for each allocation, the results, that is to
say the qualities of reception, are signaled back to the control device
23 which then generates the operating frequencies Fn1 . . . F4
simultaneously for all allocations. Due to the fact that the operating
frequencies are determined centrally by the control device 23,
interactions such as cross modulations, intermodulation products,
superpositions etc. between the individual allocations can be either
calculated or measured in a further step and taken into consideration
during the generation of the operating frequencies.